1. Field of the Invention
The present invention relates to an on-vehicle system that is mounted on a vehicle and that has a plurality of control devices, each of which is capable of communicating with each other.
2. Description of Related Art
A conventional navigation system is known to be an integral system of a navigation function and an audio-visual function, such as a function for playing CD/DVD, a function for receiving TV broadcastings, a function for receiving FM/AM radio broadcastings.
In general, the above navigation system is known to have a plurality of control devices (for example, a navigation control device, an audio control device), and, typically, the audio control device, which is one of the plurality of control devices, is connected with an on-vehicle LAN such that the audio control device is configured to communicate with an external device outside the system. Also, another control device, such as the navigation control device, is configured to retrieve information from the exterior of the system through the audio control device (for example, see JP-A-2004-196183 corresponding to US 2006/0190144).
Also, the above described system is configured to use common hardware and common software regardless of a model of the vehicle. In other words, a control device in the system stores common program shared between different vehicle models and parameters (e.g., a function to be given to an operation switch, an initial screen to be displayed in the display device) individually designed for each of vehicle models. The control device in the system selects a corresponding parameter in accordance with a signal, which is inputted from the exterior, and which is indicative of the vehicle model. When the control device executes the common program, the control device uses the above selected parameter to perform the process corresponding to each of the vehicle models.
In the above described system, in order to make each control device execute a process corresponding to a specific vehicle model, data (i.e., common data) having the above parameter is generated in advance. Then, each of the plurality of control devices of the system is configured to execute the process using the common data.
In other words, a unique program and common data are prestored in a memory of each control device. Here, the unique program achieves a certain respective function of each control device, and the common data is shared between the control devices and is designed for a specific vehicle model. Each control device executes its unique program using the common data such that each control device achieves certain functions (e.g., a navigation function, an audio function) correspondingly to a specific vehicle model. Thus, as a whole, the navigation system can correspond to the specific vehicle model.
In the above configured system, the common data is assumed to be updated for a version up as necessary. As in the above proposed system, a control device (for example, audio control device) that is connected to an on-vehicle LAN to communicate with an exterior device outside the system is connected with another control device (for example, navigation control device). In the above case, firstly, the common data of the audio control device is updated, and the common data of the navigation control device is updated through the audio control device. Thus, in order that each control device is always required to store the identical common data with each other, the common data is transmitted from the audio control device to the navigation control device at a certain time (for example, a time of activating the system) such that the common data stored in the navigation control device is updated using the common data stored in the audio control device.
However, as above, if the audio control device is configured to transmit the common data to the navigation control device at the certain time, a transmission process for transmitting the common data by the audio control device and a receiving process for receiving the common data by the navigation control device are repeatedly executed. As a result, for example, if the common data stored in each of the control devices matches with each other at the beginning, and thereby the common data of the navigation control device is not required to be updated, the transmission/reception of the common data may uselessly increase a communication load between the control devices.
Also, the above disadvantages occurs not only to the navigation system, but also to a system having a plurality of control devices that share (use) the common data.